Railway car truck friction shoe spring group

ABSTRACT

A friction shoe for a railway car truck is provided. The railway truck comprises two parallel side frames, a suspension spring assembly supported by the side frames, and a bolster transversely mounted between the side frames and supported by the suspension spring assembly. Each side frame has at least one vertical support face, and the bolster has at least one sloped support face. The friction shoe comprises a sloped wall engaging the sloped support face of the bolster, a vertical wall engaging the side frame vertical support face, and a bottom base engaging and supported by a suspension control spring group which comprises three concentrically nested coil springs which provide a normal force on the column wear plate of between 3000 and 5000 pounds in the static empty railway car truck condition and between 7,500 and 12,000 pounds force under the static loaded railway car truck condition.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates generally to railway car truck friction dampingarrangements, and more particularly to a railway car truck friction shoespring group.

The present invention is directed to a friction shoe suspension controlspring group for a railroad car truck and in particular to a suspensioncontrol spring group having three concentrically nested coil springs andto a friction shoe including a body having a sloped face and a verticalface. The suspension control spring group applies force to the frictionshoe which dissipates energy throughout the range of suspension travelthereby controlling the relative motion between the side frames andbolster as the railway car travels down the track.

Railroad car trucks of a design known as a three piece railway car truckinclude a pair of spaced apart side frames and a bolster that extendstransversely between the side frames. The bolster is resilientlysupported at each end on a respective side frame by a plurality ofsuspension springs. Wedge shaped friction shoes are used in suchrailroad car trucks to dampen movement of the bolster with respect tothe side frame of the railroad car truck. Friction shoes are usuallygenerally triangular wedge shaped such that two laterally spaced slopedfaces are each in contact with one of two laterally spaced sloped facesof the bolster. The friction shoe is also comprised of a vertical facethat is in contact with a corresponding wear plate mounted on a verticalface of a side frame column. The wear plate on the vertical column ofthe side frame is usually comprised of steel. Accordingly, the frictionshoe acts as a motion damping wedge between the bolster and the wearplate on a vertical column of the side frame.

The friction shoe also is comprised of a bottom section that joins thevertical face and the two laterally sloped face. The bottom sectionincludes a spring lug in the form of a hollow protrusion extending formthe bottom section. Such design spring lug saves weight as it has ahollow core. Further, the bottom of the spring lug is open which allowswater or other debris to pass out of the friction shoe.

The friction shoe is wedged into engagement between the sloped faces ofthe bolster and the vertical column of the side frame by a suspensioncontrol spring group. Such spring group typically comprises one or twoconcentrically grouped coil springs, or an elastomeric solid or hollowspring may comprise one or more of the springs in the spring group.Resistance to sliding movement of the friction shoe with respect to theside frame, which in turn provides dampening of vertical bolstermovement, is provided by the frictional forces generated between thefriction shoe vertical face and a wear plate on the side frame verticalcolumn. This also provides improved truck squaring capability and warpstiffness.

It is an object of the present invention to provide an improved railwaycar truck suspension control spring group and friction shoe that iscomprised of three concentrically nested springs wherein the dampingfrictional force on the vertical movement of the bolster is bettercontrolled with greater energy dissipation.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is an exploded isometric view of a railway car truck inaccordance with an embodiment of the present invention;

FIG. 2 is a detailed partial isometric view of a portion of a railwaycar truck in accordance with an embodiment of the present invention;

FIG. 3 is a isometric view of a friction shoe in accordance with anembodiment of the present invention;

FIG. 4 is a bottom view of a friction shoe in accordance with anembodiment of the present invention;

FIG. 5 is a side view of a friction shoe in accordance with anembodiment of the present invention;

FIG. 6 is an exploded isometric view of a friction shoe and spring groupin accordance with an embodiment of the present invention, and

FIG. 7 is a partial cross sectional view of an assembled spring group inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, a friction wedge 8 of the present invention isshown in a railroad car truck. The railway car truck includes two sideframes 2 which are spaced apart and generally parallel to one another.Each side frame 2 includes a bolster opening 13 formed by a pair ofspaced apart vertical columns 14. A planar wear plate 15 is connected tothe interior surface of each column 14. The railway car truck alsoincludes a bolster 1 which extends generally transversely between theside frames 2. Each end 12 of the bolster 1 is located within arespective bolster opening 13 and is vertically supported on a sideframe 2 by a plurality of helical coil suspension springs 10. Thebolster end 12 is also supported by the friction shoes 8 whichthemselves are supported by suspension control springs 9. The suspensioncontrol springs 9 and suspension springs 10 are themselves supported ona spring support section 16 of each side frame 2. Suspension controlsprings 9 and suspension springs 10 are resiliently compressible tothereby allow the ends of the bolster 1 to move vertically upwardly anddownwardly within the bolster openings 13 and with respect to the sideframes 2. Each bolster end 12 includes a plurality of sloped walls 22.Each sloped wall 22 is adapted to engage a sloped surface 20 of arespective friction shoe 8. Friction shoe 8 is seen to provide a dampingforce to the vertical motion of bolster 1 while supported on suspensioncontrol springs 9 and suspension springs 10 as the railway car travelson the rails.

Railway wheels 4 are mounted on axles 3. Axle bearings 5 are mounted onthe ends of axles 3. Bearing adaptor 6 and pad 7 are provided to receiveaxle bearings in side frame pedestal openings 2A. Center bowl 11 on thetop surface of bolster 1 is provided to help support the railway freightcar on the truck.

As best shown in FIG. 2, friction shoe 8 includes a body 17. Body 17 isgenerally triangular or wedge-shaped. The body 17 includes a base havinga generally horizontal bottom wall 34. The bottom base surface 34 isadapted to engage the top end of a set of concentrically nestedsuspension control springs 9. The body 17 also includes a generallyvertical front wall includes a front face 19. The body 17 also includesa sloped surface 29 which may be comprised of laterally spaced slopedwalls 20 and 20A that extend at an inclined angle of thirty-five toforty-five degrees between the base 34 and vertical front face 19 andapproximately 150 to 178 degrees relative to each other. Sloped surface29 is adapted to engage inclined walls 22 of the bolster 1. Theproportion of combined spring rates of the suspension control springgroup engaging with the friction shoes to the combined spring rates ofthe suspension springs engaging with the bolster is between 12 and 18percent in the empty railway car truck condition and between 20 and 27percent in the loaded railway car truck condition. A single frictionshoe inner, middle and outer coil spring provide a normal force on thecolumn wear plate of between 3000 and 5000 pounds in the static emptyrailway car truck condition and between 7,500 and 12,000 pounds forceunder the static loaded railway car truck condition.

As best shown in FIGS. 3, 4, and 5, the front face 19 of friction shoebody 17 is in direct contact with and extends from an intersection 31with bottom base surface 34. Front face 19 of friction shoe body 17 isin direct contact with and extends from an intersection with top edge 25of center spacing section 21 of sloped surface 29. Bottom base surface34 may include a spring lug 37 extending therefrom. Spring lug 37 isusually cylindrical in shape, with a bottom surface 41 of spring lug 37is flat when it engages with the inner suspension control spring 44. Thefriction shoe 8 may be made from metals such as steel or iron.

Referring now to FIGS. 6 and 7, suspension control spring group 9 isshown to comprise an outer coil spring 42, a middle coil spring 43located concentrically inside outer coil spring 42, and an inner coilspring 44 located concentrically inside middle coil spring 43.

Outer coil spring 42, middle coil spring 43, and inner coil spring 44may be comprised of steel coil springs or solid or hollow elastomericsprings. Middle coil spring 43 is seen to surround the outer cylindricalsurface of spring lug 37. Inner coil spring 44 is seen to contact bottomsurface 41 of spring lug 37 upon sufficient compressive force downwardonto spring group 9. Under empty or lightly loaded railcar conditions,spring group 9 may be uncompressed 110 and not in contact the frictionshoe bottom surface 34 or spring lug bottom surface 41.

The damping force by the friction shoe 8 can vary as may be selectedfrom the various materials for friction shoe body 17 and the force withwhich the front face 19 is impinged against side frame column wear plate15 which is directly related to the vertical force applied to the bottomof the friction shoe 8 by the suspension control spring group 9.

What is claimed is:
 1. A railway car truck comprising: two parallel sideframes, a suspension spring assembly supported by the side frames, abolster transversely mounted between the side frames and supported bythe suspension spring assembly, each side frame having at least onevertical support face, the bolster having at least one sloped supportface, and a friction shoe comprising a bottom base engaging andsupported by a support spring group, the bottom base including acylindrical spring lug extending downwardly therefrom, at least onesloped wall engaging the sloped support face of the bolster, and avertical wall engaging the vertical support face of the side frame, anda suspension control spring group having an outer coil spring, a middlecoil spring concentric within and inside the outer coil spring, and aninner spring located concentric with and inside the middle coil spring.2. The railway car truck of claim 1 wherein the inner coil spring isshorter than the middle coil spring and the outer coil spring such thatthe inner coil spring is compressed only when the railway car truck isloaded.
 3. The railway truck of claim 1 wherein the proportion ofcombined spring rates of the suspension control spring group engagingwith the friction shoes to the combined spring rates of the suspensionsprings engaging with the bolster is between 12 and 18 percent in theempty railway car truck condition and between 20 and 27 percent in theloaded railway car truck condition.
 4. The railway car truck of claim 1wherein the inner coil spring interfaces with the bottom surface of thefriction shoe spring lug.
 5. The railway car truck of claim 1 wherein acomposite facing is bonded to the friction shoe vertical support face.6. The railway car truck of claim 1 wherein a polymer wear liner isbonded to the friction shoe sloped support.
 7. The railway car truck ofclaim 1 wherein a single friction shoe inner, middle and outer coilspring provide a normal force on the column wear plate of between 3000and 5000 pounds in the static empty railway car truck condition andbetween 7,500 and 12,000 pounds force under the static loaded railwaycar truck condition.
 8. The railway car truck of claim 1 wherein thefriction shoe is comprised of cast iron.
 9. The railway car truck ofclaim 1 wherein the friction shoe is comprised of cast steel.
 10. Therailway car truck of claim 1 wherein the sloped wall of the frictionshoe extends to direct contact with the bottom base.
 11. The railway cartruck of claim 1 wherein the sloped wall of the friction shoe iscomprised of two laterally spaced surfaces with a spacing wall locatedbetween the two laterally spaced surfaces.
 12. A friction shoe for arailway car truck, the railway car truck comprising two parallel sideframes, a suspension spring assembly supported by the side frames, and abolster transversely mounted between the side frames and supported bythe suspension spring assembly, each side frame having at least onevertical support face, the bolster having at least one sloped supportface, the friction shoe comprising: a bottom base engaging and supportedby a support spring group, the bottom base including a generallycylindrical spring lug extending downwardly therefrom, a sloped wallengaging the sloped support face of the bolster, and a vertical wallengaging the vertical support face of the side frame, and wherein thefriction shoe support spring group is comprised of an outer coil spring,a middle coil spring and an inner coil spring.
 13. The friction shoe ofclaim 13 wherein the bottom base spring lug includes a hollow openingextending vertically through the spring lug.
 14. The friction shoe ofclaim 13 wherein the friction shoe support spring group is comprised ofan outer coil spring, a middle coil spring located concentric with andinside the outer coil spring, and an inner coil spring locatedconcentric with and inside the middle coil spring.
 15. The friction shoeof claim 13 wherein the friction shoe support spring group is comprisedof an outer coil spring, a middle coil spring located concentric withand inside the outer coil spring, and an inner solid elastomer springlocated concentric with and inside the middle coil spring.
 16. Thefriction shoe of claim 13 wherein the friction shoe provides a dampingforce of between 7500 and 16,250 pounds when the friction shoe is movingat a velocity of between 0 and 19 inches per second.
 17. The frictionshoe of claim 13 wherein the friction shoe provides a normal force ofbetween 2000 and 12,000 pounds.
 18. The friction shoe of claim 13wherein the friction shoe is comprised of cast iron.
 19. The frictionliner of claim 13 wherein the friction shoe is comprised of cast steel.20. The friction shoe of claim 13 wherein the sloped wall extends todirect contact with the bottom base.
 21. The friction shoe of claim 13wherein the sloped wall is comprised of two laterally spaced surfaceswith a spacing wall located between the two laterally spaced surfaces.